1. Field of the Invention
The present invention relates to a plastic cap incorporating pilfer-proof function.
2. Description of the Related Art
As is disclosed in U.S. Pat. No. 4,550,844 for example, any of those conventional plastic-molded pilfer-proof caps have a cap skirt and a band member which are integrated by means of a plurality of frangible bridges. More than 10 stopper tabs are formed on an internal wall surface of the band member by way of projecting themselves in the obliquely downward direction. When screwing the cap skirt on the bottle mouth, the stopper tabs come into contact with a bead member extending outwardly in the periphery of the bottle mouth, and then reversely bend in the obliquely upward direction. Then, while maintaining the bent condition, the stopper tabs climb over the bead member before eventually being engaged with the bottom surface thereof to prevent the band member from being lifted while opening the bottle. Each of the stopper tabs is thin at the bent end. However, the nearer the projected end, the greater the thickness of each stopper tab.
Japanese Patent Publication No. HEI3-11985 (1991) discloses a pilfer-proof cap. This prior art discloses a plurality of stopper tabs on the internal wall surface of a band member, and the stopper tabs extend in the obliquely upward direction. Like the above example, nearer the bent end, each of these stopper tabs has a thinner surface wall. This is because of the need to minimize transit resistance while the stopper tabs climb over the bead member. Excessive transit resistance causes bridges to easily be torn off while screwing the cap on the bottle mouth.
The applicant for a patent related to the present invention previously proposed a pilfer-proof cap via Japanese Laid-Open Patent Application Publication No. HEI1-182259 (1989), which provides a plurality of stopper tabs projecting from the bottom edge of a band member in the obliquely upward direction, wherein a surface wall of each stopper tab is bent in a chevron shape in a sectional view.
Each of the stopper tabs has a surface wall that is thin at the refracted end and thicker in the direction of the projected end, and the transit resistance of these stopper tabs can be minimized when climbing over the bead member on a bottle mouth. On the other hand, there is a problem in terms of the retentive force of the band member while opening the bottle cap. Accordingly, while the band member is pulled in the upward direction relative to a cap opening operation, the refracted ends and projected tips of the stopper tabs respectively bend downwardly. As a result, the band member shifts upward by such an amount corresponding to the degree of deformation incurred. In an extreme case, the band member is fully disengaged from the secured position.
If the stopper tabs were incapable of sustaining enough engaging force, even though the sealed bottles were opened out of mischief while being displayed, nobody could visually identify the earlier opening of the bottles. When the band member shifts upwardly, the seal of the cap leaves the bottle mouth before the bridges are torn off, thus resulting in the faulty effect of sealing. If this symptom occurs in a bottle containing a carbonated beverage, carbonic acid gas will be lost. Unless the bridges are torn off, dissipation of carbonic acid gas cannot be identified.
In order to provide stopper tabs with greater engaging force, for example, by increasing the thickness of the bent ends of the stopper tabs, the change would result in an increased transit resistance while the stopper tabs climb over the bead member as the cap is screwed on the bottle mouth. If excessive force were applied in order to screw the cap on the bottle mouth, the bridges could be torn off.
As is apparent from the above, it is a matter of contradiction to minimize the transit resistance while the stopper tabs respectively climb over the bead member while capping a bottle and simultaneously provide the stopper tabs with greater engaging force while opening the bottle.
On the other hand, according to the cap having the surface walls of the stopper tabs that are folded in the chevron shape, the surface walls of the stopper tabs are provided with greater buckling strength than that of conventional, plane-shaped stopper tabs, thus permitting the chevron-shaped stopper tabs to more securely retain the band member. However, like the above-cited conventional cap, the previously proposed cap is also provided with a number of independent stopper tabs on the internal surface of the band member. In consequence, these stopper tabs bend themselves inwardly or downwardly while opening a bottle thereby causing the seal to be released before the bridges are tom off. In other words, there was a certain limit in improving the strength of the stopper tabs to resist deformation during the opening of a bottle.
It is an object of the present invention to provide an improved cap incorporating a pilfer-proof function featuring minimal transit resistance while climbing over a bead member, and featuring the capability to securely retain a band member during the process of opening a bottle.
It is another object of the present invention to provide an improved cap incorporating a pilfer-proof function capable of removing the band member that is integrated with the cap itself during the process of opening a bottle.
To achieve the above objects, the present invention provides an improved plastic cap comprising a novel structure described below.
An upper cap body and a lower band member are integrally molded via a plurality of bridges disposed between them.
An annular wall extending upwardly and inwardly is integrally formed with the lower band member on an internal surface of said lower band member.
By inwardly bending an aperture edge of the annular wall in the radial direction, a plurality of stopper tabs are formed on the internal surface of said annular wall by way of projecting away from the annular wall.
The stopper tabs may be formed along the aperture edge of the annular wall by way of forming continuous chevron shapes.
According to the invention, since a plurality of stopper tabs are integrally formed with an annular wall provided on an internal surface of a band member by inwardly bending an aperture edge of the annular wall in the radial direction, a force, acting upon the band member during the process of opening a bottle, can be shared by the annular wall and the stopper tabs. In other words, since the invention increases the load sharing sectional area and provides such a bending structure that can hardly be subject to buckling deformation, the band member can be more securely retained.
When securing the inventive cap to a bottle mouth, the stopper tabs circularly shift themselves in the obliquely downward direction along a bead member. Simultaneously, only the refracted tips of the stopper tabs come into superficial contact with the bead member before receiving a radial-directional outwardly pressing reaction force, thus minimizing contact resistance. Furthermore, the stopper tabs can easily be deformed in the direction to level off the bent shape by causing the pressing reaction force to concentrate onto the bent tip ends thereof, thus minimizing transit resistance while securing the cap onto a bottle mouth.
Alternately, according to the invention, using a pair of wall surfaces that are continuous and substantially perpendicular to the aperture edge of the annular wall and another wall surface partially having circular-arc shape for interlinking the other two wall surfaces, each stopper tab is formed in the xe2x80x9c]xe2x80x9d shape, and yet, circular-arc domains may be formed between the individual stopper tabs.
When providing the xe2x80x9c]xe2x80x9d shaped stopper tabs, since a surface wall is externally pressed by the bead member when capping a bottle, the intersectional angle between the two surface walls expands in the circumferential direction to elastically deform the wall surfaces before permitting the stopper tabs to climb over the bead member. In this case, transit resistance generated in the xe2x80x9c]xe2x80x9d shaped stopper tabs is greater than that of those continuous chevron-type stopper tabs and the below-mentioned sawtoothed type stopper tabs. However, the xe2x80x9c]xe2x80x9d shaped stopper tabs generate stopper resistance (engaging resistance) that is greater than either of the above-cited continuous chevron-type and the below-mentioned sawtoothed type stopper tabs when opening a bottle.
Preferably, each of the stopper tabs has a sawtoothed shape formed by a surface wall mildly tilting to an upstream side of the cap-closing rotating direction when capping a bottle, and another short-length wall surface extending externally, substantially in the radial direction. It is also permissible for embodying the invention by way of interposing circular-arc domains between the sawtoothed stopper tabs, or by way of continuously providing the sawtoothed stopper tabs.
By virtue of the provision of the sawtoothed stopper tabs, the surface wall mildly tilting to the upstream side of the cap-closing rotating direction when capping a bottle is pressed by the bead member, and then the surface wall elastically deforms by externally expanding in the radial and circumferential directions before smoothly climbing over the bead member. After completing a bottle capping process, the wall surface returns to the original shape while being engaged with the bottom end of the bead member.
The magnitude of transit resistance generated in the course of capping a bottle with the cap incorporating the sawtoothed stopper tabs is slightly higher than that is normally generated by chevron-type stopper tabs. On the other hand, stopper resistance of the sawtoothed stopper tabs in the course of opening the cap is greater than that of the chevron-type stopper tabs, thus advantageously improving the pilfer-proof function. Furthermore, the transit resistance of the cap incorporating the sawtoothed stopper tabs can be lowered to such a degree substantially corresponding to that of the cap incorporating chevron-type stopper tabs by forming a groove at the intersection of one surface wall and another surface wall.
To embody the present invention, using a plurality of bridges each containing frail strength and a durable bridge containing durable strength, the cap body and a band member are connected to each other. A breakable domain is formed in the band member adjoining a location at which the durable bridge is provided. It is so arranged that the breakable domain and the bridges respectively have a breaking strength that is weaker than that of the durable bridge. Since the inventive cap incorporates the band member accommodating a breakable domain adjacent to a location at which the durable bridge is formed, and because the breaking strength of the durable bridge is greater than that of the breakable domain and the bridges, when opening the cap from a sealed bottle, the bridges and the breakable domain are respectively torn off except for the durable bridge that remains unaffected. After the breakable domain is torn off, the band member is disengaged from the bead member. As a result, the band member is eliminated from the bottle mouth because the durable bridge is integrated with the cap body.
According to the cap embodied by the present invention, because there is less transit resistance in the course of the stopper tabs climbing over the bead member, the actual breaking strength of the bridges can be arranged to be lower than that of conventional caps, thus saving the force needed to open up the sealed cap. Furthermore, since the band member can securely be prevented from shifting upward by way of solidly securing the band member with stopper tabs and annular walls, it is possible for the inventive cap to expedite the moment to break off the plurality of bridges. This will effectively help prevent faulty bottled products from easily being generated or otherwise caused by incidental mischief, for example. In consequence, the invention can provide useful caps capable of securely exerting pilfer-proof function as a whole.
Since the band member can also be torn off simultaneously with the breaking of small bridges during the course of opening a sealed bottle, the band member can be removed from the bottle together with the cap body.
The above and further objects and features of the invention will more fully be apparent from the following detailed description given in reference to the first through fifth embodiments and the accompanying drawings including FIGS. 1 through 11 which are merely shown by way of example.